Liquid Sealant with Thermally Adaptive Properties

ABSTRACT

A composition for sealing defects in structural materials such as roads or paved surfaces, the composition preferably comprising one or more shape memory polymer (SMP) components capable of responding to increased temperature by decreasing in volume. Smart SMP-based sealants of the invention serve to avoid adhesion failure between a sealant and the repaired structure when the repaired structure is subjected to varied temperatures that cause thermal expansion and contraction.

The benefit of the filing date of provisional U.S. application Ser. No.61/897,437, filed 30 Oct. 2013, is claimed under 35 U.S.C. §119(e) inthe United States, and is claimed under applicable treaties andconventions in all countries.

TECHNICAL FIELD

This invention broadly relates to structural materials. Moreparticularly it relates to a shape memory-based liquid smart materialfor use in repairing or sealing structural defects or cracks (such as inconcrete or asphalt pavement). Alternatively, a two-way SMP-based smartmaterial can be constructed into solid expansion panels that areinserted at the time a structure is constructed, in order to accommodatesubsequent thermal expansion and contraction yet avoiding the crackdevelopment in the structure. A shape memory-based liquid can comprise aliquid binder material along with at least one programmed shape memorypolymer (SMP) or at least one two-way shape memory polymer.

BACKGROUND ART

In asphalt pavement and concrete pavement, cracks are inevitable andcaused by: reflective cracking, thermal cracking, and fatigue cracking.Cracks allow easy access for water to reach the base, sub-base, orsubgrade. Water can deteriorate the substructure and shorten the life ofpavement substantially. When cracking has occurred, sealants aretypically applied. A goal when applying sealants is to prevent waterfrom seeping through the crack, and to prevent the entry of substancessuch as salt that might further decay base material and enlarge thecrack.

Unfortunately however, current pavement sealants commonly suffer from“adhesion loss.” When adhesion loss occurs, one or more surfaces of thesealant pull away from the crack, and consequently a crack reappears.Such separation may occur in colder seasons such as upon freezing orrapid temperature changes, and may also occur in warmer months upon asudden temperature drop such as from hail storms or rain downpours. Thisis because of the different thermal expansion properties of the sealantand the concrete/asphalt, and because the strength of sealant, itsadhesive strength and/or ductility is not large enough. In addition,during warmer months the structural material which has been repairedundergoes thermal expansion, as does the sealant itself, and this tendsto squeeze sealant out of the repaired area.

Similarly, expansion joints are weak links in bridge decks or concretepavement. Expansion joint failure is a leading cause for structuraldamage to bridge superstructures or concrete pavement. Due to thecritical role played by joints in bridge decks and pavements, crack orjoint sealants have been a topic of intensive research for many years.

Various types of sealants have been utilized to seal expansion joints inbridge decks and pavements. The most frequently used types of sealedjoints include, but are not limited to, (1) field-poured silicone andpolymer modified asphalt joints; (2) compression seal joints; (3) stripseal joints; (4) polymer modified asphalt plug joint system; (5)inflatable neoprene joints; and (6) modular joint sealing system.However, two fundamental problems continue to be challenges in thescientific and industrial community: (1) the gradually loss ofinterfacial contact, due to plastic deformation of sealant materials,and (2) sealant squeezing out of the channel in summer due to Poisson'sratio effect and thermal expansion.

Thus, there continues to be a need for structural sealants that areresistant to adhesion loss. Moreover, there is also a need for sealantswhich resist being expelled from repaired defect (or expansion joint)during thermal expansion of the repaired structure. In particular, theneed also continues for sealants that are both resistant to adhesionloss, and resistant to being expelled at warmer temperatures.

DISCLOSURE OF THE INVENTION

The present invention relates to a smart material for use to repair,seal or avoid separations, defects or cracks in a structure. The termdefect will often be used to refer to these various structural voids orimpairments. The defects can be those produced when the structureundergoes thermal expansion and contraction in its ambient environment.Alternatively, a defect can be an expansion joint separationintentionally built into the structure. The repair material comprises aconventional binding material along with at least one SMP (either aprogrammed one-way SMP or a two-way SMP). When programmed one-way SMP isused, there will be preferably be two or more programmed SMPs, andcertain preferred embodiments comprise both a tension-programmed SMP anda compression-programmed SMP.

These smart materials capitalize on SMP properties, accordingly theybehave in a manner contrary to conventional (non-SMP) physics. Thesesmart materials may contract in volume when heated, and/or expand involume when cooled. Smart SMP-based sealants of the invention serve toavoid adhesion failure between a sealant and the repaired structure whenthe repaired structure is subjected to varied temperatures that causethermal expansion and contraction. Embodiments of the invention alsohelp avoid expulsion of the sealant from a defect when there is heatingand thermal expansion of the thing repaired. Furthermore, embodiments ofthe present invention can both avoid adhesion failure as well as avoidexpulsion from the repaired defect. Also disclosed are methods formaking such compositions. In addition, methods are disclosed forcustomizing such sealing compositions to unique environments or damagecontexts. In addition, the use of a two-way shape memory polymer is setforth. Two-way shape memory polymer (due to it having two distincttemperature-related shapes) does not require programming in order tomanifest SMP properties of shrinking upon being heated and expandingwhen cooled.

In certain preferred embodiments the programmed SMP adapts to increasedtemperature by appreciable volume decrease when the temperature exceedsthe glass transition temperature of that SMP, thus behaving contrary tonormal thermal expansion. A programmed SMP with these properties isusually obtained by tension programming of a one-way SMP or by use of atwo-way SMP.

In certain embodiments, the programmed SMP adapts to increasedtemperature by appreciable volume increase as the temperature exceedsthe glass transition temperature (T_(g)) of a compression-programmedSMP; this expansion is beyond typical thermal expansion pursuant toshape memory properties. A programmed SMP with these properties isusually obtained by compression programming of a one-way SMP.

In certain embodiments, the smart liquid contains two programmed SMPcomponents. For example, a smart liquid can comprise a programmed SMPthat adapts to increased temperature by appreciable volume increase whenthe temperature exceeds the glass transition temperature of this SMP,along with a programmed SMP that adapts to increased temperature byappreciable volume decrease when the temperature exceeds the glasstransition temperature of this SMP; a preferred form of this embodimentuses an SMP that responds to increased temperature by decreasing in size(tension-programmed SMP or two-way SMP) usually having a transitiontemperature in the upper portion of an expected temperature range alongwith an SMP that responds to increased temperature by inordinateincrease in volume (compression-programmed SMP) with a T_(g) lower thantransition temperature of the other SMP. Alternatively, each of theprogrammed SMPs can be ones which adapt to increased temperature byappreciable volume decrease when the temperature exceeds the respectivetransition temperature of each SMP. A further alternative, althoughtypically less preferred, embodiment is a sealant in which eachprogrammed SMP adapts to increased temperature by appreciable (beyondthermal expansion) volume increase when the temperature exceeds therespective glass transition temperature of each SMP.

Still another embodiment comprises use of at least one two-way SMP whichinherently has two permanent shapes and has the property of shrinking athigher temperature and expanding at lower temperature. Optionally, theat least one two-way SMP can be combined with one or moretension-programmed or compression-programmed one-way SMPs. In additionto use in smart liquid sealants, two-way SMP can be used as amacroscopic solid buffer or sealant. Thus, macroscopically solid two-waySMP can be placed in an expansion joint at the time a surface orstructure is constructed.

The American Society for Testing and Materials (ASTM) has severalstandards that apply to the testing of possible materials for sealants.ASTM 5329 has over a dozen tests for these materials including:Flexibility Testing, Asphalt Compatibility, Artificial Weathering, BondTesting (Non-Immersed, Fuel Immersed, and Water Immersed), and TensileAdhesion. In certain embodiments SMP sealants of the invention fulfillone or more of the requirements set by these ASTM standards.

Exemplary embodiments of the invention include: A composition comprisingan SMP that decreases volume upon temperature increase, and a bindingmaterial, as set forth herein; this SMP can be a tension-programmedone-way SMP or a two-way SMP. A method of making a compositioncomprising a programmed SMP and a binding material, as set forth herein.A method for defining a customized a composition comprising at least oneprogrammed one-way SMP and a binding material, as set forth herein;preferably two or more programmed one-way SMPs. A method for defining acustomized a composition comprising a non-programmed two-way SMP and abinding material, as set forth herein.

DEFINITIONS

“Binder” as used herein is used to signify something that produces orpromotes cohesion in loosely assembled substances or acts cohesively.For smart liquid sealants of the invention, a suitable binder will bechemically miscible with the SMP component(s). As used herein withprogrammable SMPs, the binding material is liquid when mixed with theprogrammed SMP particles (e.g., powder or fibers); the binder-SMPmixture remains liquid prior to being injected into a defect and becomessolid upon subsequent curing. The binder must be liquid at temperaturesat and below the T_(g) of any programmed SMP component of the smartliquid. The binding material is generally conventional; examples ofsuitable binders available in the art include asphalt emulsions orsolvent diluted asphalt or rubber latex such as silicone rubber, acryliclatex, natural rubber, styrene-butadiene rubber, polyurethane, or rubbermodified asphalt emulsion.

“Decomposition Temperature (T_(D))” is defined as a temperature at whichchemical bonds are broken or violent oxidation occurs causing a materialto catch fire.

“Dual Shape SMP” is an SMP that can have two shapes: a native shape anda programmed shape. One-way SMP are generally also dual shape SMP.

“Glass transition temperature (T_(g))” describes the temperature atwhich amorphous polymers undergo a transition from a rubbery, viscousamorphous liquid (T>T_(g)), to a brittle, glassy amorphous solid(T<T_(g)). This liquid-to-glass transition (or glass transition forshort) is a reversible transition. The glass transition temperatureT_(g) is always lower than the melting temperature, T_(m), of thecrystalline state of the material, if one exists. Despite the massivechange in the physical properties of a material through its glasstransition, the transition is not itself a phase transition (a phasetransition does occur at the melting point (T_(m)), defined below);rather glass transition is a phenomenon extending over a range oftemperatures and is defined by one of several conventions. Severaldefinitions of T_(g) are endorsed as accepted scientific standards.Nevertheless, all definitions are arbitrary, and they often yielddifferent numeric results: at best, the defined values of T_(g) for agiven substance typically agree within a few Kelvin. Common synonyms forGlass transition temperature (T_(g)) include shape memory transitiontemperature (T_(trans)).

“Melting point (T_(m))”: The term melting point, when applied topolymers, is not used to suggest a solid-liquid phase transition but atransition from a solid crystalline (or semi-crystalline) phase to astill solid amorphous phase. The phenomenon is more properly called thecrystalline melting temperature. Among synthetic polymers, crystallinemelting is only discussed with regards to thermoplastics, asthermosetting polymers decompose at high temperatures rather than melt.Consequently, thermosets do not melt and thus have no T_(m). The T_(m)is what triggers the change between the two native forms of a two-waySMP.

One-way SMP is an SMP with a single glass transition temperature(T_(g)). In the absence of programming one-way SMP has onepermanent/native shape. Accordingly, if a one-way SMP is not programmedit retains the same shape immediately above or immediately blow itsT_(g). A one-way SMP has a single native form whether it iscompression-programmed or tension-programmed.

“Prestrain” is the maximum strain applied during programming.

“Relaxation time” is the time elapsed during stress relaxation process.

“Shape fixity” is similar to strain fixity, suggesting that a temporaryshape is fixed.

“Shape fixity ratio” is the ratio of the strain after programmingrelative to the prestrain.

“Strain” is defined as the change in length over the original length.

“Strain recovery” is the amount of strain that is recovered during shaperecovery process.

“Stress” is defined as the internal load per unit area.

“Stress relaxation” is a phenomenon that, once a material is deformed toa certain extent, the stress continuously reduces while maintaining thestrain constant.

“Triple-shape SMP” is an SMP that can have three shapes: a native shape,a shape where a programming “A” takes place, a shape where a programming“B” takes place. A shape where both programming “A” and programming “B”have taken place also may exist but is not counted as one of the shapes.The term “multi-shape SMP” is conceptually similar to triple-shape SMPbut generally refers to an SMP that can have more than three shapes.

“Two-way SMP” is an SMP that has two permanent shapes in the absence ofany programming. Two-way shape memory polymers change their shape uponstimulation. Many semicrystalline SMPs have demonstrated two-way shapechanging effect. During cooling under a constant stress, crystallitesform in the loading direction, leading to elongation, accordingly thereis expansion as the material is cooled. Additionally, when heated to atemperature above the melting transition of the polymer, the polymercontracts as a result of shape recovery. Thus, a two-way SMP has alarger permanent shape at a “low” temperature and a smaller permanentshape at a “high” temperature; where “low” and “high” are specified inrelation to the other. In the present invention a two-way SMP can beused any time a tension-programmed SMP is set forth unless the contextclearly indicates otherwise.

“Yield strain” is the strain corresponding to yielding. In thestress-strain curve, the change of slope signals the start of yielding.

MODES FOR CARRYING OUT THE INVENTION

In the following section “SMP” will refer to one-way programmable SMPunless the context indicates otherwise. A programmable one-way shapememory polymer (SMP) can be deformed and by programming become fixedinto a temporary shape. It will hold its temporary shape until it isheated to a temperature above its glass transition temperature (T_(g)),whereupon it will recover its original or “native” shape. Compression ofan SMP in two or three dimensions is referred to as compressionprogramming. A compression-programmed SMP is smaller in its programmedform (i.e., when below its T_(g)) and revert to its relatively largernative form (i.e., when above its T_(g)). For example, when a powderedSMP is programmed by compression in all three dimensions, the programmedSMP powder will then have the capability to respond to an increase intemperature by expanding back to its original (native or virgin) form.Conversely, by applying tension to an SMP in order to achieveprogramming (also called pulling programming or tensile programming),the programmed SMP material will have the capability to respond to anincrease in temperature by contracting back to its smaller native form.A tension-programmed SMP is larger in its programmed form (i.e., whenbelow its T_(g)) and then reverts to its relatively smaller native form(i.e., when above its T_(g)). After tension-programming the SMP can bemilled into, e.g., fibers which will exhibit diminution in size when thefibers reach the SMP glass transition temperature. Programmable one-waySMPs are often referred to as dual shape SMPs. Of note, a one-way SMPhas a single native form whether it is tension-programmed orcompression-programmed.

Mixing a compression-programmed SMP powder with a conventional liquidbinder/sealant creates a “smart” sealant that undergoes additionalexpansion (which augments normal thermal expansion) which ensures thatthere is always compressive stress between the sealant and the walls ofthe defect it is repairing: provided that the compression-programmed SMPremains at a temperature lower than the T_(g) for thecompression-programmed SMP from time of manufacture until shortly beforebeing placed into the defect. For instance, this can be achieved byusing the sealant when ambient temperature is colder than the lowestT_(g) or if the ambient temperature exceeds, T_(g), it may be applied byrefrigerating the smart sealant. In either case, the powder must bestored below its T_(g) in order to retain its programming.Alternatively, if after manufacture (at a temperature lower than thelowest T_(g) of any SMP in the composition) the sealant has beenpackaged by the volume-controlled protocol set forth herein, the sealantcan be stored and used in a temperature-independent manner; providedthat upon opening the volume-controlled container, the sealant is usedbefore the SMP programming is dissipated.

The binding material is generally conventional and is compatible withthe SMP component(s). The binding material will be in liquid form whenbeing mixed with the programmed SMP particles (e.g., powder or fibers);the binder-SMP mixture remains liquid prior to being injected into adefect and becomes solid upon subsequent curing. The binder must beliquid at temperatures at and below the T_(g) of any SMP component ofthe smart liquid; being liquid below the T_(g) this permits mixing ofthe SMP into the binder and being liquid at the T_(g) allows the SMP toregain its shape when the material reaches the T_(g). Examples ofsuitable binders are available in the art, and include asphalt emulsionsor solvent-diluted asphalt or rubber latex such as silicone rubber,acrylic latex, natural rubber, styrene-butadiene rubber, polyurethane,or rubber modified asphalt emulsion.

Embodiments Designed for Unique Environments

With the invention set forth herein, it is to be noted that the smartsealant can be designed to correspond to the particular environmentalsettings or temperatures that the repaired article will experience. Forexample, one can first identify the lowest and highest temperatures thatwill be experienced throughout the year in the structure which is to besealed/repaired. Alternatively, one can identify a particulartemperature range that is of particular concern for the maintenance ofstructural integrity. After identifying a temperature range of interest,at least two SMPs are selected (or produced in accordance withmethodologies known in the art) where one SMP has a T_(g) at or near oneend of the specified temperature range and the other SMP has a T_(g) ator near the other end of the range. Thus, a smart sealant is preparedthat counteracts the thermal expansion and contraction produced by therepaired structure when it experiences the specified temperature range.As noted above, this smart material is designed to be administered whileit is at a temperature lower than the T_(g) of the T_(g) of every SMP inthe composition.

In accordance with the invention one approach for preparing aspecialized smart sealant is to employ an SMP with a T_(g) within thedesired temperature range. When this is a programmed one-way SMP, thematerial will experience shape recovery as its temperature passesthrough the T_(g). One component of the smart composition is acompression-programmed SMP that expands when the temperature risesthrough its T_(g). A compression-programmed SMP is most useful when ithas a T_(g) in the colder portion of the temperature range. This aspectof the invention provides that the additional expansion following shaperecovery from compression programming creates a more complete matingbetween the sealant and the walls of the thing being repaired. Adhesionfailure is avoided above this T_(g) because the sealant will always havegood contact the defect wall.

Preferably, a further component of a smart sealant is another SMP thatalso has a T_(g) within the desired temperature range. However, in thiscase the second SMP will be tension-programmed. A tension-programmed SMPis most useful when it has a T_(g) in the warmer portion of thetemperature range. Preferably the T_(g) of this SMP is higher than theT_(g) of the compression-programmed SMP. The tension-programmed SMP willallow the smart sealant to shrink when the repaired thing is warmed to atemperature higher than this T_(g). Shrinkage of the smart sealantserves to avoid the sealant from being squeezed out of the defect whilethe adjacent, repaired material is thermally expanding. Alternatively,one may use a two-way SMP instead of a tension-programmed SMP toaccomplish shrinkage of the sealant at a higher temperature.

The tension-programmed one-way SMP (i.e., dual shape SMP), is preferablyprogrammed by a level of tension programming that causes the smartsealant to shrink slightly less than the thermal expansion of therepaired structure; if there were more contraction the then expansion ofthe repaired thing adhesion failure might result between the sealant andthe surface of the defect. Similarly, when using a two-way SMP, oneselects an SMP that inherently shrinks slightly less than the thermalexpansion of the repaired thing to avoid adhesion failure.

Various combinations of SMPs each with a particular T_(g) together witheither compression or tension programming can be utilized in the smartsealant. A two-way SMP can also be used alone or along with anycompression- or tension-programmed dual shape SMP. For embodiments ofthe present invention, a two-way SMP can be used any time atension-programmed SMP is set forth unless the context clearly indicatesotherwise. Accordingly, a smart sealant is generated having uniqueproperties such that it expands inordinately upon heating (above theT_(g) of a compression-programmed SMP) and/or which contracts uponheating (above the T_(g) of a tension-programmed SMP, or above the T_(m)of a two-way SMP). Accordingly, multiple embodiments of the inventionexist of which the following are exemplary:

Volume-Controlled Temperature-Independent Smart Sealant Storage

In order to effectively use the sealant, yet avoid keeping the sealantbelow the lowest T_(g) at all times between manufacture and until justbefore use, the following packaging protocol can be employed. Followingmanufacture and while the sealant is still at a temperature below thelowest T_(g), and while still below this lowest T_(g), the programmedsealant is then placed into a volume-controlled container. Avolume-controlled container is one which does not change appreciablywhen it is heated, and most importantly does not change appreciably involume when programmed SMP contained therein is at a temperature abovethe T_(g) of a compression-programmed SMP. Without being bound by theoryit is believed that increasing the temperature of a sealedvolume-controlled container with programmed SMP sealant inside providesfurther compression force (i.e., programming) to thecompression-programmed SMP particles. Therefore, packaging programmedsmart sealant in this way, then allowing the volume-controlled containedto rise to a temperature above a T_(g) for compression-programmed SMPshould not dissipate compression programming so as to worsen sealantperformance, conversely it may achieve performance improvement. For manyapplications a major issue for prior art sealants when used to repairsmall cracks/defects is low temperature debonding. The added compressionprogramming during storage has a positive effect on smart sealantperformance at low temperatures. Preferably the volume-controlledpackaged sealant is maintained at temperatures lower than the higherT_(g) (or the T_(g) of any tension-programmed SMP) in order to avoiddissipating programming of the tension-programmed SMP particles. Thesetension-programmed SMP will generally be used to address hightemperature performance so storage in this manner should still providegreat flexibility since it will generally not be the case that storagewill be at or above the highest temperature encountered in a particularenvironment.

EXAMPLES Example 1

The embodiment of this example uses two (or more) programmed dual-shapeSMPs. One SMP is compression-programmed and will generally in particlessuch as powder or fibers. The other SMP will be tension-programmed andwill generally be in fibers. The two dual-shape SMPs will have differentshape memory transition temperatures (i.e., T_(g) or T_(trans)). Thecompression-programmed SMP will have a lower transition temperature; theSMP is designed or selected to have a T_(g) within or below the low partof annual temperature range to be experienced by the repaired structure.The tension-programmed SMP will have a higher T_(g) than that of thecompression-programmed SMP. The tension-programmed SMP is designed orselected so that its T_(g) is within the upper part of the annualtemperature range experienced by the repaired structure. For example,the compression-programmed SMP will be 3-D compression-programmed and inpowder form, and the tension-programmed SMP will be 1-Dtension-programmed and in fibers.

This embodiment is designed to be administered at a temperature that islower than the lowest SMP T_(g); this can take place by storing andapplying the sealant at an ambient temperature lower than the lowestT_(g) or by refrigerating the sealant when the ambient temperatures arewarmer than this lowest T_(g). Alternatively, the smart sealant may bestored pursuant the volume-controlled temperature-independent storageprotocol discussed herein, whereby the can sealant be used at anytemperature provided it is applied to a defect before the programming isdissipated once the volume-controlled container is opened.

Without being bound by theory, it is understood that this embodimentworks as follows: The product is administered at a temperature lowerthan the T_(g) of the SMP with the lowest T_(g) i.e., thecompression-programmed SMP. Then, as the ambient temperature increases,the shape memory of the compression-programmed SMP is triggered, leadingto volume expansion. This smart sealant cold months (well beyond theproperties of typical thermal expansion), and this expansion facilitatesclose adherence of the sealant to the defect surface. This isparticularly advantageous at relatively low temperatures where therepaired structure has experienced appreciable thermal contraction. Thisexpansion offsets the movements of the repaired thing (e.g., pavement orstructure) for all temperatures higher than this T_(g) causing thesealant to remain in adhesive contact with the structure it isrepairing. Furthermore, in the warmer months the tension-programmed SMPis triggered, whereupon the SMP shrinks which causes a decrease in smartsealant volume and counteracts the expansion movement of the repairedstructure in warm periods. This tension-programmed SMP helps avoidexpulsion of the smart sealant from the defect at warmer temperatureswhen both the repaired thing (and any prior art sealant) would bethermally expanding.

Accordingly, a sealant is provided that behaves contrary to typical(non-SMP) physics in that it has expands at lower temperatures andcontracts at higher temperatures provided that the smart sealant isstored and applied to a defect at temperatures lower than the lowest SMPT_(g) so that programming forces are not dissipated. Adhesion failurecan be minimized or avoided, and that the sealant is not expelled fromthe defect at warmer temperatures.

Advantageously, temperature-based activity of the smart sealant servesto repeatedly “reprogram” the material. The expansion (at coldertemperatures) from compression programming leads to additional tensionprogramming of the fiber SMP and the SMP fiber shrinkage (at warmertemperatures) leads to additional compression programming to the SMPpowder. The system works in harmony and only initial programming of eachSMP component before manufacturing the smart sealant is needed, and thesmart sealant provides service for many thermal cycles.

For example, the powdered SMP can be epoxy-based amorphous SMPs such aspolystyrene SMP [1]. The fiber form SMP can be thermoplastic SMP such aspolyurethane [2].

Example 2

Embodiments of the invention can comprise use of triple-shape ormulti-shape one-way SMPs rather than the dual shape, one-way SMPs usedin the previous example. As used here multi-shape SMPs will includetriple shape SMPs and all SMPs have more than two programmable shapesunless it is clear the context clearly indicates otherwise. Amulti-shape SMP can be block-copolymer (or polymers with single broadglass transitions as set forth in the next embodiment). This embodimentis designed so that it has optimal effect when it is administered to adefect when the smart sealant is at a temperature lower than the lowestT_(g) amongst all SMPs. Unless this material is stored in accordancewith the volume-controlled container protocol herein, this materialshould be stored at a temperature lower than the lowest T_(g).

For triple-shape block-copolymers, (consistent with standardnomenclature) the SMP is defined as having three (3) fundamental shapes:First, a native/permanent shape (referred to here as “shape A”) in whichno programming has occurred. Second, a temporary shape (referred to hereas “shape B”) corresponding to programming of “block B”. The third shapeis also a temporary shape (shape C) which corresponds to programming of“block C”. The naming of blocks as “B” and “C” is purely forillustrative purposes herein.

For example, blocks B and C have properties as follows: block B has arelatively higher T_(g), namely a T_(g) which is within a typicaltemperature range for the warmest months; block C has a relatively lowerT_(g), namely a T_(g) which is within or below a typical temperaturerange for the coldest months.

When programming such a polymer, one begins with tension programming of“block B”, at a relatively high temperature. Once the temporary shape isfixed, the tensile-programmed material is machined to particles such aspowders or fibers, with the caveat that the machining takes place suchthat the temperature is always lower than the transition temperature ofblock B. Then, while maintaining the material at a temperature lowerthan the T_(g) of block B, 3-D compression programming of “block C” isperformed on the SMP particles. The particulate dual-programmedblock-copolymer is then mixed with a conventional liquid binder to formthe smart sealant.

For clarity, each programming will be on an already formulated blockco-polymer (and not individual blocks prior to copolymer synthesis) andthe respective programmings have effect on the relevant block in theformed polymer. Nevertheless, because of the different transitiontemperatures of the two blocks, the programming produces the maximumeffect only on a particular block at the particular programmingtemperature.

Accordingly, when this embodiment of the invention is used it isadministered to a defect when the smart sealant is at a temperaturelower than the T_(g) of block C (the compression-programmed block). Thusas the material begins to warm it will trigger the shape memory of blockC, leading to volume expansion. As the temperature of the smart sealantthen rises to the extent that it is above the T_(g) of block B, block Bis triggered and leads to shrinkage of the sealant, facilitatingretention of the smart sealant material within the defect.

Similar to the embodiment with two dual-shape SMPs, the sealantfunctions contrary to typical (non-SMP) physics—after being administeredat a temperature lower than the T_(g) of block C, as it warms thisembodiment expands inordinately (at a relatively cool temperature) andthereby facilitates adhesion between the sealant and the defect; as thetemperature increases the material contracts (now at a relatively warmertemperature) avoiding expulsion of the sealant from the defect. Theseproperties facilitate a more complete mating between the surfaces of thepolymer and the defect, and facilitate retention of the smart sealantmaterial within the defect.

As with the embodiment of the previous Example, just the initial roundsof SMP programming before manufacturing the smart sealant are required.Each thermal cycle (i.e., a rise in temperature above the respectiveT_(g) of block B and T_(g) of block C) will apply further programming tothe other programmed block; thus a temperature rise above the T_(g) ofblock B elicits shrinking/contraction of the copolymer material whichcompresses and further programs compressed block C. Conversely, atemperature rise above the T_(g) of block C elicits expansion of thecopolymer material which further programs tension-programmed block B.

For example, the block-copolymers can be:

(1) poly(ε-caprolactone) (PCL) segments and poly(cyclohexylmethacrylate) (PCHMA) segments [3],

(2) poly(ethylene glycol) monomethyl ether monomethacrylate andpoly(ε-caprolactone) dimethacrylate [4],

(3) graft-polymer network from poly(ε-caprolactone)-dimethacrylates(PCLDMA) as macrocrosslinkers and poly(ethylene glycol) monomethylether-monomethacrylate (PEGMA) forming the grafted side chains having adangling end [5], or

(4) poly(co-pentadecalactone) and Poly(ε-caprolactone) segments as aVersatile triple-Shape Polymer System [6].

For example, referring to document [3], the poly(ε-caprolactone) (PCL)will be “block B” crystallites which contribute to the fixed strain of“shape B” and the polyethylene glycol (PEG) will be “block “C”crystallites which contribute to the fixed strain of “shape C” (in thispolymer the formation of low-melting temperature PCL crystallites duringcooling also contributes to the fixation of shape C).

Example 3

As noted above, the invention comprises use of multi-shape SMPs. Theform of multi-shape SMP used in the present Example is one that has asingle yet broad glass transition. The broad glass transition allows fordiscrete programmings at different temperatures within this broad glasstransition range. For the purpose of this sealant embodiment, a polymeris selected which has a glass transition range which is broader than orcovering a desired portion of the annual temperature range of materialto be repaired.

The programming process is analogous to that for block-copolymers, setforth in the previous Example 2. Here, one starts withtension-programming of the SMP at a temperature corresponding to theparticular warm annual temperatures, e.g., a temperature above whichthermal expansion of the repaired thing would cause expulsion of a priorart sealant from the repaired defect. After that, the tension-programmedSMP is machined to particles such as powder or fibers while keeping thematerial at a temperature below the tension-programming temperature.After this, the particles are 3-D compression-programmed at atemperature corresponding to cooler yearly temperatures. Once thetwo-step programming is completed, the dual-programmed SMP is mixed withcompatible liquid binder to form the smart sealant of the invention.

As with the embodiment of the previous Example, just the initial roundsof SMP programming before manufacturing the smart sealant are required.Each thermal cycle (i.e., a rise in temperature above the respectiveprogramming temperature in the broad T_(g) will apply furtherprogramming to the portion of the SMP programmed in the alternative(compression or tension) manner; thus a temperature rise above theprogramming temperature used for a tension programming elicitsshrinking/contraction of the SMP material which compresses and furtherprograms the portion of the material subject to compression programming.Conversely, a temperature rise above programming temperature in theT_(g) utilized for compression programming elicits expansion of the SMPwhich further programs tension-programmed portions of this material.

For example, the SMP with a single broad glass transition can be apolytetrafluor-oethylene backbone and perfluoroether sulphonic acid sidechains [7].

Example 4

The liquid smart sealant repair material of this Example has two or moredual-shape SMPs. For this embodiment the SMP is milled short fibers. Thetwo or more dual-shape SMPs will have distinct shape memory transitiontemperatures (i.e., T_(g)), and each SMP has a T_(g) within the desiredthermal range. In this embodiment, each of the two or more SMPs will be1-D tension-programmed.

This smart sealant can preferably be at its most compact when it is at atemperature just higher than the highest T_(g) for any of the two ormore SMPs, and the material can be at its most voluminous at atemperature just lower than the lowest T_(g) for any of the two or moreSMPs. It is to be understood that normal thermal expansion andcontraction are taking place on this smart sealant as well; thus it ispossible, e.g., upon heating the smart sealant for normal thermalexpansion to be greater than volume decrease obtained by passing throughthe T_(g) of a tension-programmed SMP. It is often preferable that thevolume decrease obtained by heating through the T_(g) of one of thetension-programmed SMP to be greater than normal thermal expansionthereby producing a relative volume decrease for the material as it isheated: this helps avoid the sealant from being expelled from therepaired defect upon heating. Conversely, it is generally preferablethat the volume increase obtained by cooling through the T_(g) of one ofthe tension-programmed SMPs to be greater than normal thermalcontraction, thereby producing a relative volume increase for thematerial as it is cooled: this facilitates the sealant remaining inadhesive contact with the defect surface as the material is cooled.

Without being bound by theory, it is understood that this embodiment ofthe invention works in the following way: The product is administeredsuch that the sealant is below the lowest T_(g) of any SMP. If thematerial is stored in a volume-controlled container, it may beadministered at any ambient temperature with the understanding that uponopening the volume-controlled container, the programmed smart materialis applied to a defect before the sealant has time to expand anddissipate its programming. Thus, as the sealant material is heated andpasses through a T_(g) of each tension-programmed SMP, the smartmaterial will undergo sequential contractions. Conversely, as thematerial is cooled and there is any SMP in the sealant that has a T_(g)lower than this starting temperature the smart material will undergotension-programming-related expansion as its temperature falls below anysuch T_(g). Here we have a sealant that behaves entirely against normal(non-SMP) physics and expands as it is cooled. This feature allows thematerial to remain in contact with the adjacent cracked surface throughtemperature fluctuations, and thereby counteracts the contraction of thestructural materials (e.g., pavement) in colder months, and itcounteracts the expansion of the structural materials in warmer months;this provides that adhesion failure can be minimized or avoided, andthat the sealant not expelled from the defect at warmer temperatures.

Although not to the extent of the embodiment set forth in Example 1(which had both compression-programmed and tension-programmed SMPs),temperature-based activity of the structure being repaired serves to“reprogram” the SMPs in this smart material. The normal thermalcontraction of the repaired structure at colder temperatures leads toadditional tension programming of the SMP in this embodiment. Therefore,with only initial programming of each SMP component beforemanufacturing, the smart sealant of the invention provides service formany thermal cycles.

For example, the fiber form SMP can be thermoplastic SMP such aspolyurethane [2].

Example 5

The embodiment of this Example comprises use of multi-shape SMPs. Thetriple- or multi-shape SMPs can be block-copolymers (alternatively,polymers with single broad glass transitions as set forth in the nextembodiment). For block-copolymers, consistent with standardnomenclature, the SMP is defined as having 3 fundamental shapes: First,a native/permanent shape (shape A) in which no programming has occurred.Second, a temporary shape (shape B) corresponding to programming of“block B”. The third shape is also a temporary shape (shape C) whichcorresponds to programming of “block C”. The naming of blocks as “B” and“C” is purely for illustrative purposes herein.

This embodiment is designed so that the sealant can be administered atany ambient temperature. Accordingly, in the present embodiment blocks Band C can have properties as follows: block B has a relatively highertransition temperature (T_(g)), generally a T_(g) which is within atypical temperature range for the warmest months; block C has arelatively lower glass transition temperature (T_(g)), a T_(g) which iswithin a typical temperature range for the coldest months of the year.In this embodiment all blocks are tension-programmed. The multipleprogrammings are accomplished by methodologies known to those ofordinary skill in the art. Once the temporary shape is fixed for each ofthe blocks, the tensile programmed material is machined to particlessuch as fibers, with the caveat that the machining takes place so thatthe temperature is always lower than the lowest T_(g) of any block. Thenow fibrous dual-programmed or multiply-programmed block-copolymer isthen mixed with a conventional liquid binder to form the smart sealant.

As a point of explanation, this programming is on the entire blockco-polymer (and not individual blocks prior to copolymer synthesis).Each block in the copolymer is tension-programmed as the temperaturefalls from above to below the T_(g) of that particular block, and thissingle programming has effect on each relevant block in the entirepolymer.

Without being bound by theory, it is understood that this embodiment ofthe invention works in the following way: The product is administeredsuch that the sealant is below the lowest T_(g) of any SMP block. If thematerial is stored in a volume-controlled container, it may beadministered at any ambient temperature with the understanding that uponopening the volume-controlled container, the programmed smart materialis applied to a defect before the sealant has time to expand anddissipate its programming. Thereafter, as the material is heated, andany programmed SMP block in the copolymer has a T_(g) higher than thisstarting temperature the smart material will undergo contraction as itis heated through any such T_(g). Conversely, as the material is cooledand there is any SMP block in the copolymer that has a T_(g) lower thanthis starting temperature the smart material will undergo some expansionas its temperature falls below such T_(g). The behavior of the smartsealant counteracts the typical thermal contraction or expansion takingplace in the material/structure that is being repaired when the repairedstructure undergoes changes in temperature.

Accordingly, here we have a sealant that behaves entirely against normal(non-SMP) physics and it expands as it is cooled. This feature allowsthe material to remain in contact with the adjacent cracked surfacethroughout temperature fluctuations, and thereby counteracts thecontraction of the structural materials (e.g., pavement) in coldermonths, and it counteracts the expansion of the structural materials inwarmer months. Accordingly, adhesion failure is minimized or avoided,and the sealant not expelled from a defect at warmer temperatures, andvoids between the smart sealant and the repaired surface is minimized oravoided during colder temperatures.

Although not to the extent of the embodiment set forth in Example 2(which had both compression-programmed and tension-programmed SMPblocks), just the SMP programmings, before manufacturing the smartsealant is required. Temperature-based expansion/contraction activity ofthe structure being repaired serves to “reprogram” the block copolymerSMP in the smart material. For example, the normal thermal contractionof the repaired structure at colder temperatures leads to additionaltension programming of the fiber SMP in the smart sealant. Therefore,only initial one-time programming of each SMP component(s) beforemanufacturing smart sealant is needed, and the smart SMP-binder sealantof the invention provides service for many thermal cycles.

For example, the block-copolymers can be poly(ε-caprolactone) (PCL)segments and poly(cyclohexyl methacrylate) (PCHMA) segments [3],poly(ethylene glycol) monomethyl ether monomethacrylate andpoly(ε-caprolactone) dimethacrylate [4], graft-polymer network frompoly(ε-caprolactone)-dimethacrylates (PCLDMA) as macrocrosslinkers andpoly(ethylene glycol) monomethyl ether-monomethacrylate (PEGMA) formingthe grafted side chains having a dangling end [5], andPoly(ω-pentadecalactone) and Poly(ε-caprolactone) Segments as aVersatile triple-Shape Polymer System [6]. For example, for reference[3], the poly(ε-caprolactone) (PCL) will be “block B” crystallites whichcontribute to the fixed strain of “shape B” and the polyethylene glycol(PEG) will be “block “C” crystallites which contribute to the fixedstrain of “shape C” (in this polymer the formation of low-meltingtemperature PCL crystallites during cooling also contributes to thefixation of shape C).

Example 6

As with the embodiment discussed in Example 3, this embodiment utilizesan SMP that has a single yet broad glass transition, and this allows oneto program the polymer at different temperatures within this broad glasstransition range. For the purpose of this smart sealant embodiment, apolymer is selected which comprises a glass transition range which isbroader than (or covers a key portion of) the annual yearly temperaturerange experienced by the material sought to be repaired.

The programming process is analogous to that for block-copolymers setforth above where all programming is tension programming. This SMP isprogrammed in accordance with methodologies known to those of ordinaryskill in the art. For example, one can program the SMP by applyingtension while at a temperature higher than the upper end of the T_(g)range, then while tension continues to be applied, one cools thematerial until it is cooler than the low end of the T_(g) range. As thecooling occurs, this serves to sequentially program the SMP at differenttemperatures within the T_(g) range. Once the temporary shape is fixed,this material now with multiple tension-programmings, is machined toparticles such as fibers, with the caveat that the machining takes placesuch that the temperature is always lower than the low end of the T_(g)range for this SMP. The fibrous multiply tension-programmed polymer isthen mixed with a conventional compatible liquid binder to form thesmart sealant. Preferably, this material will behave entirely contraryto normal (non-SMP) physics such that the material will expand as itcools and contract as it is heated.

For example, the SMP with a single broad glass transition can be apolytetrafluor-oethylene backbone and perfluoroether sulphonic acid sidechains [7].

Example 7 Structural Sealant with a Single Dual Mode Programmed SMP

The following exemplary steps are followed in accordance with thepresent Example:

1. Convert solid SMP to powder form

2. Compression program the powdered SMP

3. Mix programmed SMP powder with liquid binding material

4. Pour SMP-liquid binding material mixture(s) into asphalt structureswhich contain a predefined defect (crack)

5. Allow specimens to cure several hours, to permit waterremoval/evaporation from the asphalt emulsion

6. Put specimens through multiple cycles of defined heating (above T_(g)of the SMP), room temperature stabilization, then cooling and freezing(below T_(g) of the SMP)

7. Visually inspect specimens for integrity of the sealant itself, andany separation between the sealant and the repaired material.

Materials:

Containers for the asphalt specimens consist of 6 inch inner diametersteel pipe with male threads on one end. Each pipe is 2″ long. The pipeis then screwed into a female receiving piece which is firmly affixed toa 7″×7″ steel plate. The threads of the pipe and those of thecorresponding receiving piece are such that they allow the pipe to bescrewed onto the plate so that the end of the pipe is in direct contactwith the flat plate, creating a generally liquid tight seal.

Conventional paving asphalt specimens are obtained which are tubular inconfiguration, with a circular cross-section having a diameter ofapproximately 6″ and a length of approximately 2″. Each asphalt specimenis composed of two essentially identical halves. Thus, when the twoparts are configured together; such specimen is essentially circular incross section, and each of the two parts being just under one-half thecross section, i.e. a semi-circle. They are just less than one-half ofthe diameter of the pipe in order that a “defect” exists between the twohalves. When the halves of each asphalt specimen are configured togetherwithin the pipe container per this protocol, a “defect” is establishedbetween the two abutting flat surfaces. The “defect” runs across thecenter diameter of the cross section and extends the length of thespecimen.

The two halves of each asphalt specimen are inserted into the pipe whichhas now been affixed to the steel plate. When so assembled, the “defect”between the halves is approximately 0.02″ wide when the curved sides ofeach half are firmly against the inner surface of the pipe. Preferably,the gap is maintained by spacers that run the length of the specimen,the spacers also ensure that the outer curved surface of each of thetwo-part asphalt specimens is in full, firm contact with the innersurface of the pipe. For example, the spacers can be pieces of steelwire that are 0.02″ in diameter.

A styrene based SMP is made, in accordance with procedures known in theart, from vinylbenzene ReagentPlus ≧99% (Sigma-Aldrich, St. Louis, Mo.),vinyl neodecanoate (Sigma-Aldrich, St. Louis, Mo.), and divinyl-benzene,technical grade, 80% (Sigma-Aldrich, St. Louis, Mo.) with Luperox® A98,benzoyl peroxide, reagent grade, ≧98% (Sigma-Aldrich, St. Louis, Mo.) asthe radical initiator. The T_(g) of the styrene-based SMP is 60° C.

A Ball Mill PQ-N2 4×500 mL Gear-Drive Planetary (Across International,New Jersey, USA) was used to fabricate the SMP particles. The power ofthe machine is 750 W. The powders are taken out from the jar after 12hours of milling. It is noted that ball milling applied 3-D compressivestress to the powder. Therefore, no additional 3-D compressionprogramming was conducted on the powders.

Then, to create sealants in accordance with the invention, programmedSMP is mixed with standard liquid asphalt binder/sealant. One example ofa binder is Speed-Fill™, product code 6438-9-34 (Black Jack Asphalt SealInc., Saginaw, Mich., USA); it can provide repair on cracks and jointsup to ¾″ wide. This Speed-Fill™ crack filler is an example of aconventional fast drying product to be used in accordance with theinvention, e.g., one which is suitable for use in the repair ofstructural materials such as concrete, asphalt roads, driveways,pavements, expansion joints and walkways.

To create the sealant for “specimen A”, enough programmed SMP is mixedwith standard liquid asphalt binder/sealant to create a mixture with 5%SMP.

To create the sealant for a “specimen B,” the above materials are usedwith the difference that enough programmed SMP is mixed with thestandard liquid asphalt binder/sealant to create a 10% SMP mixture.

To create the sealant for “specimen C” no SMP as added to the standardliquid asphalt binder/sealant, it is simply standard liquid asphaltsealant and it serves as a control.

Methods:

Accordingly steel pipes are affixed to the steel plates as set forthabove, then the two-part asphalt specimens are inserted into the pipes,and then gaps are maintained by inserting spacers, the respectivesealants (A, B, C) are added. To create specimens A, B, and C, therespective sealants were slowly poured into the respective defect suchthat the defect is fully occupied with sealant.

Each defined heating and cooling cycle consists of three phases: heated,room temperature, and frozen. Heating of the specimens occurs such as inan oven to a temperature above the T_(g) (60° C.) of the SMP component.Once a temperature above T_(g) is achieved, it is maintained for 60minutes. The next phase of the temperature cycle involves removing thespecimen from the oven, and then allowing it to achieve roomtemperature; once room temperature is achieved the specimen ismaintained at room temperature for 60 minutes. The next phase of thetemperature cycle involves placing the now room temperature sample intoa freezer until the specimen is below freezing (0° C.), and maintainingthe specimen at this sub 0° C. temperature for 60 minutes.

After each cycle the specimens are inspected for any loss of adhesion.The respective specimens are then each subjected to the specifiedheating-stabilizing-freezing cycles until any loss of adhesion is notedin any sample.

Specimen C is the first to show loss of adhesion between the walls ofthe defect and this control sealant. Advantageously, at this same extentof testing, neither specimen A (5% SMP) nor specimen B (10% SMP) showsigns of any loss of adhesion between the walls of the defect and therespective sealant.

Upon visual inspection of the three specimens after these temperaturecycles, the sealant (a, b, c) within in each of the specimens remainsintact.

Example 8 Two-Way SMP-Based Smart Sealant

The present embodiment utilizes the same concept, addressed in moredetail herein, that a key advantage for a smart sealant is that it canbehave opposite to usual non-SMP physics, i.e., the desired material isable to expand when cooled and contract when heated. Accordingly, setforth is an alternative shape memory polymer-based smart sealant, whichcomprises a two-way shape memory polymer.

As compared to one-way shape memory polymer, which needs programming toform the temporary shape, two-way shape memory polymer has two permanentshapes and does not need programming to achieve more than one shape.Two-way shape memory polymers change between their permanent shapes uponstimulation. Many semicrystalline SMPs have two-way shape changingeffect. During cooling, with the proviso that there is at least someconstant stress, crystallites form in the loading direction; this leadsto elongation and expansion of the material as it is cooled.Additionally, when heated to a temperature above the melting transitionof the polymer, the polymer undergoes shape recovery, contracts andthereby reverts to the other permanent form.

Therefore, when such two-way SMPs are used as a component of astructural sealant, the sealant composition lengthens when cooled andshortens when heated; this is exactly the type of behavior desired forsealant in order to counteract the thermal expansion and contraction ofthe item being repaired. For comparison, this is conceptually analogousto the shape behavior obtained in tension-programmed one-way SMPs whichalso become smaller upon being heated.

For instance, we set forth a two-way SMP panel than can be inserted in ajoint channel during construction of the surface material (e.g.,asphalt, concrete, metal, composite or polymeric structural materials).The panel also comprises a ductile adhesive to bond with the adjacentstructure. During service, when the expansion panel reaches the hightemperature that elicits one permanent shape, the SCP-based expansionpanel shrinks and thereby avoids having the panel either squeeze out ofthe channel or crush the surrounding structure. Additionally, when thetemperature drops, the structure, through the ductile adhesive appliesthe small tensile load needed to allow the 2-way SMP sealant to increasein size when cooled and thus take the form of its other permanent shape.Accordingly, once the structure reaches the low temperature that elicitsthe other permanent shape, the panel expands and avoids loss of contactwith the structure wall.

2) In addition, we set forth a two-way SMP that is machined intoparticles (e.g., powders or fibers) and mixed with a liquid binder(e.g., asphalt emulsion or solvent diluted asphalt), to form a smartliquid sealant. This embodiment is useful in sealing cracks in astructure that form after construction, such as thermal cracks, fatiguecracks, reflective cracks, block cracks, alligator cracks, etc.

Example 9

The performance characteristics of a desired sealant can be identifiedwhen a person knows or hypothesizes the following: the dimensions of thecrack/defect (width, depth), the length of the neighboring concreteslabs, the coefficient of thermal expansion of the concrete, the lowesttemperature expected to be encountered, the highest temperature expectedto be encountered, as well as the temperature at which the sealant is tobe installed. The temperature parameters are of particular importance.

The performance of the sealant depends on several factors, such as thevolume fraction of the SMP particles, the prestrain level duringprogramming, the coefficient of thermal expansion of the SMP and theasphalt matrix, the interfacial bonding strength, etc. In accordancewith methodologies known to those of ordinary skill in the art, thesedesign parameters can be adjusted depending on the requirements of thedefect to be sealed.

For the discussion immediately below, subscripts designate as follows inTable 1:

TABLE 1 Subscript letter (lower case) Reference (c) Concrete (d) Defect(h) High (i) Installation (l) Low (s) Sealant

Therefore, in order to prepare a sealant for use in a particularenvironment we know or specify each of the following parameters:

the length of the concrete slabs L_(e),

the defect width W_(d),

the defect depth D_(d),

the temperature of the sealant when it is installed T_(i),

the lowest temperature to be encountered in the environment T_(l),

the highest temperature to be encountered in the environment T_(h),

the coefficient of thermal expansion of the SMP sealant α_(s), and

the coefficient of thermal expansion of the concrete α_(c).

With these specifications (and working on the assumptions that thetemperature is uniform throughout the filled defect and the concrete,and the objects are free to move) we can estimate the shrinkage (S) ofthe concrete slabs (S_(e)) and asphalt sealant (S_(s)) during winter inthe horizontal direction according to the following formulae in Table 2:

TABLE 2 Material Shrinkage Formula Concrete S_(c) = L_(c) (T_(l) −T_(i))α_(c) Sealant S_(s) = W_(d) (T_(l) − T_(i))α_(s)

In order to compensate for the combination of these shrinkages, thesealant should expand at least the same amount. Therefore, the recoverystrain (ε_(winter)) of the sealant in the winter (which is e.g.,controlled by the compression-programmed SMP with lower T_(g)) is:

$ɛ_{winter} = {\frac{\left( {S_{c} + S_{s}} \right)}{W} \times 100\%}$

Analogously, we can also estimate the vertical recovery strain that isneeded to take care of the squeezing out problem in the summer. Assumingthe Poisson's ratio of the sealant is “ν”, the displacement movement (d)of the sealant in the vertical direction due to the combined expansionsof the concrete pavement and thermal expansion of the sealant is:

d=L _(c)(T _(h) −T _(i))α_(c)ν+0.5D _(d)(T _(h) −T _(i))α_(s)

The vertical recovery strain required in the summer is:

$ɛ_{summer} = {\frac{d}{0.5D_{d}} \times 100\%}$

For example, we may plan to seal concrete pavement cracks in anenvironment such as found in Baton Rouge, La. To do so, the followingparameters are specified: L_(c)=6 m, W_(d)=1 cm, D_(d)=10 cm, T_(i)=0°C., T_(l)=−5° C., T_(h)=40° C., α_(s)=3.2×10⁻⁴/° C., α_(c)=1.4×10⁻⁵/° C.With these parameters, the calculations provide the recovery strain(ε_(winter)) of the sealant in the winter should be ε_(winter)=4.36%.Accordingly, our smart sealant should have a recovery strain of 4.36%,so that the sealant will maintain contact with the concrete wall withoutdebonding during the winter. For isotropic materials, volume change is3-times the linear dimension change, which yields a volume changeincrease of 13.1% for winter.

Furthermore, the desired recovery strain for the sealant during summermonths (ε_(summer)) is calculated. The desired vertical recovery strainis calculated based on the same parameters used in the winter-relatedcalculations, and the assumption that the Poisson's ratio of the sealantis 0.4. Accordingly, the vertical recovery strain is to be:ε_(summer)=3.968%; this is controlled e.g. by the tension-programmed SMPwith the higher T_(g). For isotropic materials, volume change is 3-timesthe linear dimension change, which yields a volume decrease is3×3.968%=11.9% for summer.

CITATIONS USED IN EXAMPLES

-   [1] G. Li and T. Xu. Thermomechanical characterization of shape    memory polymer based self-healing syntactic foam sealant for    expansion joint. ASCE Journal of Transportation Engineering, Vol.    137, No. 11, pp. 805-814, (November, 2011).-   [2] G. Li, H. Meng, and J. Hu. Healable Thermoset Polymer Composite    Embedded with Stimuli-responsive Fibers. Journal of the Royal    Society Interface, Vol. 9, No. 77, pp. 3279-3287, (December, 2012).-   [3] Bellin I, Kelch S, Langer R, Lendlein A. Polymeric triple-shape    materials. Proceedings of the National Academy of Science of USA    2006; 103:18043-18047.-   [4] Bellin I, Kelch S, and Lendlein A. Dual-shape properties of    triple-shape polymer networks with crystallizable network segments    and grafted side chains. Journal of Materials Chemistry 2007; 17:    2885-2891.-   [5] Behl M, Bellin I, Kelch S, Wagermaier W, Lendlein A. One-Step    Process for Creating Triple-Shape Capability of AB Polymer Networks.    Advanced Functional Materials 2009; 19:102-108.-   [6] Zotzmann J, Behl M, Feng Y, and Lendlein A. Copolymer Networks    Based on Poly(w-pentadecalactone) and Poly(ε-caprolactone) Segments    as a Versatile Triple-Shape Polymer System. Advanced Functional    Materials 2010; 20, 3583-3594.-   [7] Xie T. Tunable polymer multi-shape memory effect. Nature 2010;    464:267-270.

The complete disclosures of all references cited in this application arehereby incorporated by reference, as is the complete disclosure ofpriority application Ser. No. 61/897,437. In the event of an otherwiseirreconcilable conflict, however, the present specification shallcontrol.

What is claimed:
 1. A composition for repairing defects in a material,said composition able to respond to heating by decreasing in volume,wherein said composition comprises: at least one SMP capable ofundergoing temperature-related alteration in shape unrelated to phasechange whereby this at least one SMP is able to respond to heating bydecreasing in volume upon the temperature exceeding its transitiontemperature; and, a binder compatible therewith.
 2. A composition ofclaim 1 wherein the at least one SMP capable of undergoingtemperature-related change is tension-programmed one-way SMP.
 3. Acomposition of claim 1 wherein the at least one SMP capable ofundergoing temperature related non-phase change alteration in shape istwo-way SMP.
 4. A composition of claim 1 further comprising acompression-programmed one-way SMP, whereby this compression-programmedSMP undergoes a temperature-related, non-phase change alteration inshape producing an increase in volume beyond that from thermal expansionwhen heated to a temperature higher than the transition temperature. 5.A composition of claim 1 wherein the at least one SMP is a blockco-polymer.
 6. A composition of claim 1 wherein the at least one SMPcomprises a one-way SMP with a glass transition temperature ofsufficient range such that this SMP is able to concurrently exist in twoor more programmed states.
 7. The composition of claim 6 wherein theone-way SMP has a glass transition temperature of sufficient range suchthat this SMP is able to concurrently exist in a compression-programmedstate and a tension-programmed state.
 8. A composition in accordancewith claim 1, wherein said composition comprises: at least onetension-programmed SMP able to respond to heating by decreasing involume; and, at least one compression-programmed SMP able to respond toheating by increasing in volume.
 9. A composition for use in sealing adefect in a structure expected to experience a particular temperaturerange, said composition comprising: a tension-programmed SMP having aT_(g) in the expected temperature range; and, a binding material.
 10. Acomposition of claim 9, said composition comprising: thetension-programmed SMP having a T_(g) in the expected temperature range;a compression-programmed SMP having a T_(g) lower than the T_(g) of thetension-programmed SMP; and, a binding material.
 11. A composition ofclaim 9, said composition comprising: at least two non-identicaltension-programmed SMPs each having a T_(g) in the expected temperaturerange.